The long term goal of the proposed research is to utilize electrophysiological and psychophysical techniques as a means of studying those mechanisms of the human visual system in the normal and diseased state which pertain specifically to pattern (spatial) vision. The research program will include: (1) The electrophysiological recording of the visually evoked potential using a pattern stimulus of constant mean luminance and the use of psychophysical measures (preferential looking behavior) to follow the development of pattern vision in preterm and term infants; and to use these data to determine when the human visual system matures and when critical periods occur, particularly with regard to spatial vision; (2) Recording of visually evoked potentials and the psychophysical measurement of vision in infants and young children who have been visually deprived because of congenital cataracts, strabismus, anisemetropia, ptosis and corneal opacities in order to measure the rate of development of pattern vision in the affected eye(s) and to establish critical periods for treatment. (3) Recording of the electroretinogram and visually evoked potential in response to a patterned stimulus of constant mean luminance in adults with MACULAR and OPTIC NERVE DISEASE as a means of differentiating between macular and optic nerve disease. Data obtained under these conditions will aid in determining how spatial vision is affected in the diseased state and increase our general understanding of the basic mechanisms underlying spatial vision in the normal visual system.